Combination assembly for managing a hose or like elastic pump tube in a positive displacement pump

ABSTRACT

A combination assembly is disclosed for managing a hose or like elastic pump tube or pump channel such that particularly is used in a peristaltic pump. The invention is characterized by having the pump equipped with an assembly for the adjustment of the pump pressure and/or compression imposed on the hose/tube, the assembly comprising a steplessly adjustable eccentric adjustment mechanism.

The present invention relates to a combination assembly according to thepreamble of claim 1 for managing a hose or like elastic pump tube orpump channel such that particularly is used in a positive displacementpump.

Positive displacement pumps, in which peristaltic pumps form a subclass,are employed for pumping problematic substances in particular, such asabrasive, corrosive, slurried or high-viscosity liquids andliquid-suspended solids. Peristaltic pumps are also preferred whenpumping as a primary function must be complemented with accuratemetering, high hygienic standard and leakproofness. Peristaltic pumpsare used widely, e.g., in the manufacture of foodstuffs, drugs, oil andchemical products. In heavy industries, peristaltic pumps serve to pump,i.a., such materials as liquids and ore/mineral suspensions.

To operate properly, a peristaltic pump must be capable of forcing avolume of a fluid medium to move along a hose/tube by way ofperistaltically compressing the hose from end to end during one turn ofthe pump rotor while simultaneously the next fluid volume is alreadyfilling the hose. Conventionally, this pumping sequence is implementedby rotating a nonrotary shoe or pressing roller, whereby the hose issubjected to progressive compression in the nip between the shoe/rollerand the peripheral wall of the pump head. Furthermore, thehose/tube/tubing is selected to be sufficiently elastic and reinforcessuch that the hose resumes its circular profile immediately after thecompression thereby creating a vacuum in its lumen thus inducing theentry of the next volume of the fluid medium into the hose.

Most generally, this pump construction is implemented by way of flexinga straight hose/tube into a semicircle adapted into the pump head cavitywherein the hose is compressed radially by two diametrically oppositeshoes or rollers. This kind of pump embodiment is characterized in thatthe shoe or roller applies a compressive force against the hose at alltimes and that the pump is typically half filled with a lubricant (e.g.,glycerin) serving both to transfer frictional heat to the pump'sexternal housing structures and therefrom out from the pump as well asto reduce sliding or rolling friction occurring in the compression ofthe hose. However, at higher rotor speeds or operation against a highhead, the pump heats up so much that it must be stopped at regularintervals for cooling down. If the pump is specified for continuousoperation, the pump as well as the drive motor/gear must beoverdimensioned resulting in substantial investment and operating costs.Additional costs are also incurred during service and adjustment of thepump inasmuch as the lubricant must be drained and replaced at the sametime as the seals of the pump housing and shaft are replaced.

Moreover, in this kind of prior art construction, both ones of the rotorshoes/rollers begin to compress the hose at its suction end thusimparting a transient force impulse on both the stationary hose fixtureand the hose itself. Such an impulse occurring twice during a singleturn of the pump rotor imposes strong stresses on the hose andparticularly the captive fiftings of the hose ends.

In some pump constructions, attempts have been made to reduce the highabrasive friction and rapid pulsation by way of using compressing wheelrollingly running in bearings along an orbital trajectory. Herein, thehose may be bent into a full circle or even more, whereby the hosesuction and discharge ends overlap. This kind of a single-contactrolling wheel minimizes the friction between the compressing wheel andthe hose thus needing substantially less lubrication. Moreover, thesingle-contact pump rotor running over a full circle of the hose halvesthe number of pumping pulses, that is, only one fluid pulse instead oftwo is ejected from the pump per one turn of the rotor. Fluid pulsationalso remains less aggressive due to the larger compressive area of therotor that closes the lumen of the hose at a respectively slower speedresulting in slower onset/fall of the fluid pulse than in double-contactpumps. This kind of construction also has less friction and, hence,generates less heat thus facilitating continuous operation at a higherrotor speed, whereby the desired volumetric flow rate can be producedwith a smaller pump, gear train and motor.

However, continuous operation at a high speed is strenuous to both thehose and, in particular, the captive fittings of the hose ends. Hence, atypical problem in prior-art positive displacement pumps of theperistaltic type is associated with the captive securing of the hoseends to the pump housing. The hose is conventionally fixed with hoseclamps/inserts to a support flange mounted to the external side of thepump housing. The captive securing of the hose ends must take the linepressure imposed on the pump, seal the hose feedthrough opening so thatthe medium serving as hose lubricant in the pump does not leak out fromthe pump housing and, simultaneously, fix the hose to the pump housingso tightly that the forces imposed by the rotor on the hose cannotpull/push the hose end free.

The state of the art is represented, e.g., by patent publicationFR-1114877 disclosing a construction in which a roll is adaptedorbitally rotatable in the pump cavity by means of a crankshaft. Thepump structure is illustrated in FIG. 2 of cited reference publication.It must be noted that the elastic pump flow channel does not cover afull 3600 circle in the pump cavity.

In patent publication AU-19971675, “Orbital peristaltic pump withdynamic pump tube,” is disclosed an oscillatory compressive ring adaptedrotatable in the pump cavity by alternative drive means. The tube ispassed a full 360° circle along the inner periphery of the pump cavityand the suction/discharge ends of the tube enter/leave the pump cavityin a tangential fashion relative to the pump housing. The cross sectionof the tube is shown in FIG. 6 of cited reference publication.

A crucial problem hampering prior-art constructions is the total lack ofan adjustment mechanism for setting the compressive force. Morespecifically, no facility is provided for setting the compressionapplied on the pump hose or like elastic flow channel, whereby thedistance between the rotor and the pump cavity cannot be varied from aconstant value. In addition to the shortcomings listed above,conventional embodiments of the captive fitting of the hose to the pumphousing are often implemented in an extremely awkward fashion. In otherwords, the technical implementation in regard to its practicablefunctionality and everyday servicing has mostly been neglected entirely.

Almost invariably, the above-mentioned problems are associated with eachother and often in an intimate causal relation to each other. Hence, itappears to be extremely essential for efficient and service-friendlyoperation of a peristaltic pump that further attempts are made todevelop a system featuring simple and reliable captive fitting of thehose as well as an adjustment mechanism of the hose compression.

It is an object of the present invention to overcome the abovedisadvantages. The goal of the invention is attained by means of acombination assembly for managing a hose or like elastic pump tube orpump channel, in particular such a hose/tube that is used in a positivedisplacement pump.

The specifications of an assembly according to the invention aredisclosed in the characterizing parts of appended claims. The inventiondiffers from the prior art by virtue of having the pump equipped with anassembly suited for the adjustment of the pump pressure and/orcompression imposed on the hose/tube, the assembly featuring a mechanismwith steplessly adjustable eccentricity. In addition to this feature,the invention is characterized in that the peristaltic pump is adaptableto use, either alone or in conjunction with the eccentric adjustmentmechanism, a captive hose fitting system for managing the pressureimposed on the pump hose/tube.

In the following, the invention is described in more detail by makingreference to the appended drawings in which

FIG. 1 is an illustration of an embodiment of a peristaltic hose pump;

FIG. 2 is a cross-sectional side elevation view of an eccentricadjustment mechanism according to the invention adapted to a peristalticpump;

FIG. 3 is a cross-sectional front elevation view of an eccentricadjustment mechanism according to the invention set into its uppermostposition;

FIG. 4 is a cross-sectional front elevation view of an eccentricadjustment mechanism according to the invention set into its lowermostposition;

FIG. 5 is a cross-sectional view of an eccentric adjustment mechanismaccording to the invention;

FIG. 6 is a longitudinally sectional view of a captive hose fittingsystem according to the invention adapted to a peristaltic pump; and

FIG. 7 is a cross-sectional view of a captive hose fitting systemaccording to the invention adapted to a peristaltic pump.

Referring to FIG. 1, therein are shown the main components of aperistaltic pump. The pump comprises a pump body 1, a hose 2 and a rotor3 mounted freely rotatable on bearings mounted onto an eccentricadjustment bushing 5. The eccentric adjustment bushing in turn ismounted on a crankshaft pin denoted by reference numeral 10 of FIG. 2.The crankshaft is mounted on bearings on the rear wall of pump body 1,centrally in regard to the pump cavity 34. The hose or like elastic pumptube or pump channel is inserted into the pump cavity with the rotorhoused therein, whereby the hose rests against the pump cavity innerperimeter so as to cover a full circle. The hose ends are captivelyfitted in feedthrough openings 8 of the pump body. Actuated by the drivemeans, the crankshaft forces the rotor to rotate in the pump cavity at agiven distance from the interior perimeter of the pump cavity. Thisdistance is set smaller than the two-fold thickness of the hose/tubewall. Hereby, the rotor compresses the hose inserted in the pump cavityso that, with the rotation of the rotor, the volume of fluid mediumbeing pumped and contained in the hose in front of the rotor isprevented from leaking in the reverse direction past the point of thehose compressed by the rotor. With the rotation of the rotor in the pumpcavity, it rolls over the hose surface thus propelling the bulk of fluidmedium contained in the hose. With the rotary progressive motion of therotor and the hose recovering its circular profile immediately after thepoint of rotor compression, the hose creates a vacuum that causes thehose to become refilled with the fluid medium being pumped.

In FIGS. 2, 3 and 4 is shown an eccentric adjustment mechanismcomprising an eccentric adjustment bushing 5, a worm gear 6, a spur gear9, a lockcover 4, lockpins 11 and locking bolt(s) 12. The eccentricadjustment mechanism serves to adjust the gap 23 shown in FIG. 4 betweenthe rotor outer surface and the pump cavity inner periphery thatdetermines the compressive force imposed on the hose. The rotor gap isadjusted by rotation of the eccentric bushing 5 mounted on thecrankshaft pin 10. The rotor in turn is mounted on a bearing on theouter periphery of the eccentric bushing. The eccentricity 19 of theadjustment bushing illustrated in FIG. 3 is accomplished by drilling thebore of the bushing eccentrically in regard to the outer periphery ofthe bushing.

The rotation of the eccentric adjustment bushing takes place with thehelp of a reduction gear such as a worm gear adapted between theeccentric bushing and the crankshaft. The reduction gear is constructedby adapting the worm 6, i.e., the driving shaft of the reduction gear,into the solid body part of the eccentric bushing. The spur gear 9,i.e., the driven gear, is mounted to the end of the crankshaft pin.Alternatively, the driven spur gear 9 may also be machined directly tothe end of the crankshaft pin. With the rotation of the driving shaft,the eccentric bushing turns on the crankshaft pin, whereby the distance23 between the rotor outer periphery and the pump cavity inner peripherychanges as shown in FIG. 4. The maximum possible span of pumprotor-to-body distance adjustment is equal to the difference betweenwall thicknesses 20 and 21 of bushing 5 as shown in FIG. 3.

A worm gear or like self-locking gear is advantageously used as thereduction gear. This allows the rotor gap adjustment to be carried outaccurately and easily by a single operator, since the compressive forceapplied to the hose cannot rotate the bushing backward inasmuch as theself-locking reduction gear prevents uncontrolled rotation of thebushing. Based on the use of a toothed reduction gear, the rotor gapadjustment can be performed without the need for any special tools oradjustment shims.

In a running pump, the eccentric adjustment bushing is continuallysubjected to forces that tend to rotate the eccentric bushing. With thehelp of lockcover 4, the eccentric bushing is locked to the crankshaftpin so that the reduction gear need not take all the rotational forcesdirected to the eccentric bushing during the operation of the pump. Thelockcover is clamped against a conical surface 14 of the eccentricbushing with a bolt 12 illustrated in FIG. 2 to pass through thelockcover and fit into a threaded hole 22 of the crankshaft end shown inFIG. 3. In addition to providing the locking force of the conical fit,the tightened bolt presses a sealing O-ring 15 placed between thelockcover flange and the eccentric bushing in order to prevent the hoselubricant or other contamination from entering into the reduction gearand the interface between the eccentric bushing and the crankshaft pin.Thus, the screws passing through the lockcover only serve to provide theclamping force that keeps the lockcover tight against the conicalsurface 13. The force, which tends to rotate the eccentric bushing andis transmitted via the conical interface between the lockcover and theeccentric bushing, is transmitted further to the crankshaft end via thelocking between the crankshaft and the lockcover. This locking isaccomplished with the help of lockpins 11 sunken in the crankshaft endor a key slot. The lockcover is respectively provided with recesses 13mating with the lockpins or key.

By virtue of the lockcover, also the inner races of the bearings mountedon the eccentric bushing can be clamped axially between a shoulder 17 ofthe eccentric bushing and a shoulder 16 of the crankshaft. This isnecessary to clamp the inner races of the bearings in a stationary andtight fit between the shoulders of the eccentric bushing and thecrankshaft thus preventing the bearings from having a play in regard tothe eccentric bushing.

A characteristic property of a peristaltic pump based on positivedisplacement is that the inner surface of the hose/tube erodes duringpumping. This process reduces the hose wall thickness and, thence, thecompression of the hose in the gap between the pump rotor and body.Hence, the hose compression must be adjusted during the life of thehose. During continuous use, the known wall thickness of the hose wearsdown to an unknown value. In such a situation, it is very difficult toestablish valid rules to be applied in conventional techniques ofcorrect adjustment of hose compression. Invalid adjustment rules must becomplemented with practical operating experience that frequently invokesserious overcompression and pump damage situations. In contrast, theeccentric adjustment assembly disclosed in the present applicationallows runtime adjustment of hose compression to be carried out simplywith a calibrated torque wrench. The end 18 of the worm is so shaped asto be rotatable by means of the torque wrench. As the worm is thusturned with the torque wrench, an accurately set torque can be appliedduring rotation of the worm. With the applied torque thus being alwaysconstant, also the compressive force imposed on the hose becomessufficiently accurately set to a constant value. In the adjustment ofhose compression, it is important to apply a constant tightening torqueat all times in order to compensate for slackening compression due tothe wear of the hose.

In FIG. 3 the eccentric adjustment is shown set into its minimumcompression gap position. In FIG. 4 respectively, the eccentricadjustment is shown set into a position wherein the compression gap 23is set to its maximum value.

In FIG. 5 is shown an alternative embodiment of the eccentric adjustmentassembly according to the invention. This modification of the adjustmentassembly is suited for setting the hose compression particularly insmall-size pumps in which the adoption of the above-describedreduction-gear-based adjustment arrangement is not economically orphysically viable.

The eccentric adjustment assembly of FIG. 5 comprises a locknut 25 atthe crankshaft end, a lockcone 27 and an eccentric bushing 5. In thisembodiment, the hose compression adjustment is based on the sameeccentric adjustment concept as described above and illustrated in FIG.2. The principal differences between these two embodiments are seen inthe technique of providing the torque for rotating the cone bushing andin the arrangement for locking the eccentric bushing in place. Rotationof the eccentric bushing on the crankshaft pin takes place by turningthe bushing by the keyhead of its flange with a conventional wrench ortongs. The eccentric bushing is locked into the desired adjustmentposition by the lockcone 27. The lockcone is pressed home by way oftightening the locknut 25 onto an outer thread 26 made on the crankshaftend. The locknut is secured to the shaft with a tab washer. The lockconeis detached with the help of extractor threads 24 made on the flange ofthe lockcone. To this end, the lockcone flange is provided with twothreaded holes 24 wherein extractor bolts can be fifted to remove thelockcone. The bolts are tightened until their tips meet an innershoulder of the eccentric bushing, whereby they force the eccentricbushing off from its place. For precise hose compression adjustment,between the tab wafer and the eccentric bushing may be placed a dialplate with a graduation needed in the adjustment. The dial plate issecured to the shaft with the help of the same key slot as is used forsecuring the tab washer.

A captive hose fitting system complementing the assembly according tothe invention is shown in FIGS. 6 and 7. The captive system comprises arubber flange 32 inserted to the hose end, seal gills advantageouslycomprising two gills 33, and two halves of a split collet 28 and amounting flange 7 that may be replaced by a conventional piping flangeif so desired.

the outer perimeter of the hose, at opposite sides thereof relative toeach other. The cross section of the seal gills is made 0.5 to 1 mmthicker than the width of the slits 34 made to the collet as it isdivided into two halves.

The feedthrough opening in the pump body is of the same size or slightlylarger than the outer diameter of the hose end flange 32 inserted to thehose end. To mount the hose into the pump cavity, the hose end is passedfrom inside the cavity outward via the feedthrough opening. The lengthof the free hose end projecting out from the feedthrough opening istrimmed to about twice the hose thickness. The split collet 28 is placedabout the hose end, behind the hose end flange 32, so that the sealgills 33 remain trapped between the split collet halves. Next, theflange of the split collet is fitted against the hose end flange alreadyinserted to the hose end. To the rear side of the flange of the splitcollet is placed an O-ring 29. Finally, the hose end is pushed back intothe pump cavity so deep that the flange of the split collet remainsresting against the pump body 1. Then, the O-ring placed on the splitcollet remains compressed in the gap between the flange of the splitcollet and a bevel 30 made to the edge of the feedthrough opening of thepump body thus exerting a force that presses the halves of the splitcollet against the seal gills. Resultingly, a seal is establishedbetween the perimeter of the split collet and the pump cavity. Thecaptive fitting set comprising the hose end flange, the split collet andthe O-ring is tightened with the help of mounting screws 7 against therim of the feedthrough opening made on the pump body. To accommodate thehose end flange, the mounting flange has a sunken shoulder 31 madethereon serving to prevent overtightening of the hose end flange. Thedepth of the sunken shoulder is dimensioned such that the mountingflange meets the flange of the split collet at a depth where thecompression of the hose end flange at the hose end is about 30%. Thisamount of compression is sufficient to keep the hose end firmly clamped.Excessive compression of the hose end flange damages the hose end flangethus impairing the strength of the flange. In certain cases, the fixingholes of the mounting flange can be drilled into the same positions asthose of a standardized piping flange corresponding to the nominal sizeand pressure specifications of the pump. Then, the mounting flange canbe replaced by a conventional piping flange if so desired.

A steel ring embedded in the hose end flange further assures that thehose end flange retains its shape and the flange cannot slip off fromits captive position even under heavy mechanical stress. The seal gills,which provide the sealing of the longitudinal gaps between the halves ofthe slit collet employed in the clamping of the pump hose, also serve asindicators during the mounting of the pump hose to verify that the pumphose is clamped straight, not in a twisted position. The seal gills arecast such that they are in a horizontal position when the pump hose iscorrectly mounted.

To a person skilled in the art it is obvious that the invention is notlimited by the above-described exemplifying embodiment, but rather maybe varied within the inventive spirit and scope of the appended claims.In addition to those described above, more benefits are obtained byvirtue of the constructions implemented in the assembly of theinvention. The captive hose fitting system provides simple andpull-resistant securing of the pump hose. The arrangement disclosedherein permits the use of a flanged hose and sealed feedthrough of thehose. The hose fitting system also facilitates correct and easy mountingof the hose and verification of the mounting. Additionally, it allowsthe use of a standardized piping flange to be used for pump connections.

Respectively, the benefits and inventiveness of the eccentric adjustmentassembly are appreciated, i.a., in reliable and accurate setting of hosecompression force also on a worn hose. The eccentric adjustment bushingassembly the bearing to be tightened lashless onto the eccentric bushingwith the help of the lockcover and, further, locking of the eccentricbushing and sealing of the compression adjustment gear with the help ofthe lockcover. All the adjustments can be carried out by a singleoperator without the need for special tools and storage of multiplespare parts separately.

The assembly according to the invention represents a substantialadvancement in the construction of a peristaltic pump as to itsefficiency, operational reliability and, in particular, ease of service.The invention is characterized in that the assembly disclosed hereinrelates to the pumping of liquids and slurries by way of progressivelycompressing an elastic hose, starting from the hose suction end andfinishing at the hose discharge end, whereby the progressive compressiontransfers forward the liquid or slurry volume in front of thecompression point. Both of the mechanical constructions described aboveare advantageously utilized in the assembly according to the invention.The object of the invention is particularly directed to a novel andinventive approach to inserting the pump hose into the pump cavity, acaptive fixing system for the hose ends, a replacement method of thehose giving minimized downtime, and an adjustment/locking mechanism ofthe compression applied to the hose.

1. A combination assembly for managing a hose or like elastic pump tubeor pump channel as used in a peristaltic pump, characterized in that thepump is equipped with an assembly for the adjustment of the pumppressure and/or compression imposed on the hose/tube, the assemblycomprising a steplessly adjustable eccentric adjustment mechanism. 2.The combination assembly of claim 1, characterized in that theperistaltic pump is adaptable to employ, either alone or in conjunctionwith the eccentric adjustment mechanism, a captive hose fitting systemfor managing the pressure imposed on the pump hose/tube.
 3. Thecombination assembly of claim 1, characterized in that the eccentricadjustment mechanism comprises an eccentric adjustment bushing (5), aworm gear (6), a spur gear (9), a lockcover (4), lockpins (11) and atleast one locking bolt (12).
 4. The combination assembly of claim 3,characterized in that the eccentric adjustment mechanism is employed toadjust the gap (23) between the pump rotor outer surface and the pumpcavity inner periphery by way of rotating the eccentric adjustmentbushing (5) mounted on the crankshaft pin (10).
 5. The combinationassembly of claim 3, characterized in that the eccentricity (19) of theeccentric adjustment bushing is accomplished by drilling the bore of thebushing eccentrically in regard to the outer periphery of the bushing.6. The combination assembly of claim 5, characterized in that therotation of the eccentric adjustment bushing is accomplished by means ofa reduction gear adapted between the eccentric adjustment bushing andthe crankshaft, the reduction gear being constructed by adapting theworm gear (6) into the solid body part of the eccentric adjustmentbushing.
 7. The combination assembly of claim 4, characterized in that aspur gear (9) is mounted to the end of the crankshaft pin or,alternatively, is machined directly to the end of the crankshaft pin. 8.The combination assembly of claim 3, characterized in that theadjustment force of hose compression is controlled using a calibratedtorque wrench for rotating the worm gear (6) at its end (18).
 9. Thecombination assembly of claim 4, characterized in that the eccentricadjustment bushing is locked to the crankshaft pin with the help of thelockcover (4) that is clamped against a conical surface (14) of theeccentric adjustment bushing with a bolt (12), whereby simultaneouslythe force imposed by the tightened bolt presses a sealing O-ring (15)placed between the lockcover flange and the eccentric adjustmentbushing.
 10. The combination assembly of claim 4, characterized in thatthe rotation of the lockcover is prevented with the help of the lockpins(11) placed between the crankshaft pin end and the lockcover.
 11. Thecombination assembly of claim 4, characterized in that, by virtue of thelockcover, also the inner races of the bearings mounted on the eccentricadjustment bushing are clamped axially between a shoulder (17) of theeccentric adjustment bushing and a shoulder (16) of the crankshaft. 12.The combination assembly of claim 2, characterized in that the captivehose fitting system comprises a rubber flange (27) inserted to the hoseend, seal gills advantageously comprising two gills (33), and two halvesof a split collet (28) and, optionally, a mounting flange (7).
 13. Thecombination assembly of claim 12, characterized in that the seal gills(33) are made to project from the hose end flange in a form with thediametrical dimension across the outer edges of the seal gills matchingthe outer diameter of the hose end flange and the seal gills beingsituated about the outer perimeter of the hose, at opposite sidesthereof relative to each other, whereby the cross section of the sealgills is made 0.5 to 1 mm thicker than the width of the slits (34) madeto the collet as it is divided into two halves.
 14. The combinationassembly of claim 12, characterized in that the feedthrough opening madeon the pump body is of the same size or slightly larger than the outerdiameter of the hose end flange (32) inserted to the hose end and thatthe split collet is placed about the hose end flange, behind the hoseend flange (32), so that the seal gills remain trapped between the splitcollet halves.
 15. The combination assembly of claim 12, characterizedin that the flange of the split collet is fitted against the hose endflange inserted to the hose end and that to the rear side of the flangeof the split collet is placed an O-ring (29), which becomes compressedin the gap between the flange of the split collet and a bevel (30) madeto the edge of the feedthrough opening of the pump body thus exerting aforce that presses the halves of the split collet against the seal gillsand seals the gap between the split collet and the pump body.
 16. Thecombination assembly of claim 12, characterized in that to the mountingflange is made a sunken shoulder (31) serving to prevent overtighteningof the hose end flange.